"I consider the statement of the general staff an attempt of a military coup. I am inviting all our supporters to the Republic Square right now. I will soon address the nation live," Pashinyan said Thursday on Facebook, according to state news agency Armenpress.
Onik Gasparyan, the army's chief of general staff, issued a statement earlier in the day criticizing Pashinyan's decision to sack Tiran Khacharyan, the army's first deputy chief of the general staff.
Gasparyan called for Pashinyan's resignation and said the prime minister's cabinet should also step down.
"The prime minister and the government are no longer able to make reasonable decisions," the army statement said.
"For a long time, the Armenian Armed Forces were patiently tolerating the "attacks" by the incumbent government aimed at defaming the armed forces, but everything has its limits," the statement added, according to Armenpress.
The statement was signed by Gasparyan, his deputies, and top military commanders who make up the general staff of the Armenian armed forces.
State media reported that the general staff said the government's "ineffective" administration and "serious mistakes in foreign policy" had led the country to the brink.
"The army has always been with the people, just like the people are with the army," the statement added.
Thousands gathered in Armenia's capital, Yerevan, to support the Prime Minister after he denounced the military broadside, according to Reuters.
The crisis follows months of criticism targeting Pashinyan over his handling of Armenia's war with Azerbaijan last year in the disputed area of Nagorno-Karabakh.
In November 2020, Pashinyan announced he had signed an "unspeakably painful agreement" with Russia and Azerbaijan to end the war, just hours after Azerbaijan claimed it had captured the region's strategic city of Shusha.
Anti-Pashinyan demonstrations started after he signed the agreement. The protesters at one point entered the parliament building and assaulted the president of the National Assembly, but tensions have calmed in the months since.
Kremlin spokesman Dmitry Peskov said in a conference call with journalists on Thursday that Russia is following the developments with "concern" but that the matter was an internal matter for the Armenian government.